I'm only para 1400, but I find UE to be better for T13 farming than Impale. Goldwrap and Boon of the Hoarder makes you invincible, you're doing more than enough damage to handle elites comfortably AND clearing screens of trash and breakables at the same. And with Avarice band you're grabbing all the gold as you go, stopping only for DB's and legendaries.
This weekend Arkismall was talking about a topic similar to this on stream - they were talking about split bounties, and he said that "on non-season even with paragon 4000 we're not doing T13, we're doing T12 because it's more efficient". It's funny that a player who has achieved rank 1 spots and is one of the best-geared and highest paragon players on non-season isn't running T13, but people with maybe a fraction of that power think they can handle T13. Sigh. I can't wait for 2.6.1 when UE on T13 becomes viable because right now almost no one should be doing T13.
Impale can do T13, but it's way to long to do bounties with it. Appart from bosses, regular bounties are slow with impale because it's a badAOE build. UE is the best to farm bounties but can't do T13 efficiently right now.